Semiconductor device and its manufacturing method

ABSTRACT

For manufacturing a semiconductor device, such as thin-film solar battery, comprising a base body made of an organic high polymer material, an oxide electrode film and semiconductor thin film each containing at least one kind of group IV elements on the oxide electrode film, one of the semiconductor thin films in contact with the oxide electrode film is stacked by sputtering in a non-reducing atmosphere such as atmosphere not containing hydrogen gas, for example. Thereby, it is ensured that granular products as large as and beyond 3 nm are not contained substantially at the interface between the oxide electrode film and that semiconductor thin film. Therefore, a semiconductor thin film such as amorphous semiconductor thin film can be stacked with enhanced adherence on a plastic substrate having an oxide electrode film like ITO film on its surface.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a semiconductor device and itsmanufacturing method and, more particularly, to a semiconductor deviceusing a plastic substrate suitable for application to a thin-film solarbattery, for example.

[0003] 2. Description of the Related Art

[0004] In case of using fossil fuel like coal and petroleum as an energysource, carbon dioxide as its exhaust product is considered to inviteglobal warming. Using an atomic energy involves a danger of radioactivecontamination. In these days where environmental issues are beingdiscussed, it is not desirable to rely on these energies.

[0005] Solar batteries that are photoelectric conversion elements forconverting sunlight to electric energy have almost no effects on theearth environment, and their further diffusion is anticipated.Currently, however, there are some problems that disturb theirdiffusion.

[0006] There are a lot of materials of solar batteries. Among them,solar batteries using silicon are commercially available. They aregenerally classified to crystalline silicon solar batteries usingmono-crystalline silicon or polycrystalline silicon and amorphoussilicon solar batteries. Heretofore, monocrystalline or polycrystallinesilicon has been often used for solar batteries. However, although thesecrystalline silicon solar batteries have a higher conversion efficiencythat indicates the performance of converting photo (solar) energy intoelectric energy than amorphous silicon, much energy and time wererequired for crystalline growth. Therefore, it was difficult tomass-produce them and provide them inexpensively.

[0007] Amorphous silicon solar batteries currently have a lowerconversion efficiency than crystalline silicon solar batteries. However,they have advantageous features, such as the need for only a smallthickness of less than one hundredth of the thickness that a crystallinesilicon solar battery needs for photoelectric conversion, which exhibitsa high photo absorption property of amorphous silicon solar batteriesand enables formation of a solar battery by stacking a relatively thinfilm; the capability of selecting as a substrate various materials likeglass, stainless steel, polyimide plastic films, and so on, making useof the amorphous quality; readiness of making a battery of a much largerextension; and so on. Furthermore, it is considered that themanufacturing cost can be lowered than that of crystalline silicon solarbatteries, and future diffusion over a wide range from the home uselevel to a large-scaled power plant level is anticipated.

[0008] In the structure of an amorphous silicon solar battery,development of CVD technologies has made it possible to produce cells bysequentially stacking semiconductor thin films of desired compositionsand thicknesses. In general, often used cells have a structure having apotential gradient from the photo detecting surface to the back surface,which is made by sequentially stacking on a substrate of glass, forexample, n-type hydrogenated amorphous silicon (hereinafter called“a-Si:H”) thin film containing phosphorus, a [p-type] i-type a-Si:H thinfilm containing no impurity, and a p-type a-Si:H thin film containingboron.

[0009] In addition to such structure having a potential gradientproduced by impurities, also known are hetero junction type solarbattery cells that have a structure including a multi-layered film madeby stacking two or more kinds of semiconductor materials different inband gap and are capable of efficient photoelectric conversion matchingwith different wavelengths, as a technology for fabricating ahigh-efficiency amorphous solar battery.

[0010] Regarding hetero junction type solar battery cells, there is atrial of effectively using light by employing hydrogenated amorphoussilicon germanium (hereinafter called “a-SiGe:H”) thin film, forexample. This a-SiGe:H has a high photo absorptance, and allows anincrease in short-circuit current. However, since a-SiGe:H has morelevels in a band gap than a-Si:H, it has the drawback that slope factorsdecrease. Thus, the band gap is continuously changed by changing thecomposition ratios of a-SiGe:H, a-Si:H or the like of the i-type layer,to overcome those drawbacks. In case of this structure, as the minimumvalue portion of the band gap of the i-type layer comes closer to thep-type layer on the part of incidence of light, light deteriorates lessand the device can be improved in reliability. This is because alongwith an increase of the photo absorption distribution near the p-typelayer, collection of holes is improved more. However, making the minimumband gap portion near the p-type layer involved the problem that theband gap of the i-type layer near the p-type layer became smaller andrendered the open circuit voltage lower. Further, although this methoddecreases the band gap of the i-type layer and increases the opticalabsorption, decreasing the band gap of the i-type layer to about 1.4 eVor less causes slope factors to decrease, and the efficiency is notimproved even with an increase of the amount of photo absorption.Furthermore, there is known the method of interposing hydrogenatedamorphous silicon carbide (hereinafter called a-SiC:H) film having awide gap around 2.1 eV between the p-type layer and the i-type layer forthe purpose of further improving the open circuit voltage.

[0011] On the other hand, an amorphous film fabricated at a substratetemperature of or below 200?C contains a number of elements like localenergy levels in the energy band gap, which can be nucleus ofrecombination of minority carriers, and its carrier length is shorterthan those of single crystals and poly-crystals. If the darkconductivity becomes small in doped a-Si:H, a-SixGel-x:H, a-Ge:H,a-SiC:H and other like films, conversion efficiency of solar batteriesusing these films as their p-type layers and/or n-type layers of pindiodes forming the solar batteries become lower, and this is a bar tofabrication of high-quality solar batteries at low temperatures.However, also proposed is the technology of increasing the darkconductivity by using laser annealing which crystallizes only p-typelayers and/or n-type layers of pin diodes while keeping substrates atlower temperatures.

[0012] Appropriate combination of these technologies is expected toimprove the efficiency of amorphous silicon solar batteries, and furtherdiffusion of amorphous silicon solar batteries in the future isanticipated also from the standpoint of their manufacturing cost.

[0013] In order to provide for various future uses of solar batteriesfor wide-spreading amorphous silicon solar batteries, decreasing theweight of products, improvement of their productivity, reduction of thecurvature processing cost, and others, are required. Many of materialshaving low melting points and plastic materials can be configured intodesired shapes at low temperatures, and are therefore advantageous inreadiness to reduce the processing cost. Plastic materials have furtheradvantages that products are light and not fragile. Therefore, it isdesirable to make high-quality amorphous silicon solar batteries orhetero junction type solar batteries on substrates of those materials.

[0014] If plastics, especially general-purpose plastics like polyesterfilms, can be employed as base bodies, those requirements can be met incombination with roll-to-to-roll production facilities using elongatedbase bodies.

[0015] However, when films are stacked on a plastic substrate, thesubstrate is liable to curve or warp after growth of the films due to astress in films caused by difference in thermal expansion coefficientbetween the plastic and films, swelling of the plastic, and so on. Inthis case, if the films grown on the plastic substrate insufficientlyadhere one another, films will peel off at their boundaries.Additionally, although the stress of the films exerted to the substratecan be relaxed by simultaneously stacking films on opposite surfaces ofthe substrate, if the films do not adhere well, it is not possible tomake the most of flexibility of the plastic.

[0016] Plasma CVD has been typically used heretofore as a technology forfabricating photovoltaic devices using amorphous silicon films or otherlike films. Plasma CVD typically uses SiH4 as the source material gas.In the case where the film is stacked on ITO as a transparent electrodeby plasma enhanced CVD (PE-CVD) using SiH4, SiH4 gas is decomposed inthe plasma into hydrogen ions and damages the ITO surface. In case of asolar battery using a conventional glass substrate, the substrate doesnot warp with a stress of the film after deposition of the film, and thesolar battery is not bent in practical use. Therefore, separation of thesubstrate and the film did not occur. A plastic substrate, however,warps with a stress from a film after deposition of the film. An a-Sifilm stacked thereon will undesirably peel off at the boundary with ITO.

[0017] Taking account of photovoltaic property of a film and itsdeposition rate, deposition of a film by PE-CVD is indispensable, andthis is very serious problem upon fabricating a solar battery on aplastic substrate.

[0018] Toward a solution of the above-indicated problems involved in theconventional techniques, the Inventor made various researches that aresummarized below.

[0019] As already explained, conventional manufacturing method ofphotovoltaic devices using amorphous silicon films, or the like, usuallyprovide very good thin films if the films are stacked by using plasmaCVD.

[0020] There is also a deposition method by sputtering as one ofdeposition methods of amorphous silicon films. In case of stacking afilm by plasma CVD, since it uses SiH4 as the source material gas, itinevitably exposes the substrate surface to H2 plasma. However,sputtering is conducted without introducing H2 gas, this problem can beavoided.

OBJECTS AND SUMMARY OF THE INVENTION

[0021] This invention has been made through further researches by theInventor based on the knowledge reviewed above.

[0022] To attain the above-indicated object, according to the firstaspect of the invention, there is provided a semiconductor devicecomprising:

[0023] a base body made of an organic high polymer material;

[0024] an oxide electrode film on the base body; and

[0025] a semiconductor thin film on the oxide electrode film, whichcontains at least one kind of group IV elements,

[0026] wherein no granular products each having a diameter not smallerthan 3 nm are substantially contained at the boundary between the oxideelectrode film and the semiconductor thin film.

[0027] From the viewpoint of further improving the adherence between theoxide electrode film and the semiconductor thin film, it is preferablethat the boundary between the oxide electrode film and the semiconductorthin film does not contain granular products with a diameter not smallerthan 1 nm.

[0028] According to the second aspect of the invention, there isprovided a semiconductor device comprising:

[0029] a base body made of an organic high polymer material;

[0030] an oxide electrode film on the base body; and

[0031] a semiconductor thin film on the oxide electrode film, whichcontains at least one kind of group IV elements,

[0032] wherein the semiconductor thin film is stacked in a non-reducingatmosphere in an initial period of deposition thereof.

[0033] According to the third aspect of the invention, there is provideda manufacturing method of a semiconductor device having a base body madeof an organic high polymer material; an oxide electrode film on the basebody; and a semiconductor thin film on the oxide electrode film, whichcontains at least one kind of group IV elements, comprising:

[0034] a step of stacking the semiconductor thin film in a non-reducingatmosphere in an initial period of deposition thereof.

[0035] In the present invention, the base body is typically atransparent base body, and more specifically, a film of a transparentorganic high polymer material such as polyester (PET), for example, isused. The oxide electrode film is typically a transparent electrodefilm, and more specifically, it is, for example, ITO (indium tin oxide),tin oxide, tin oxide doped with fluoric acid, zinc oxide, zincoxide-aluminum oxide, or the like.

[0036] In the first aspect of the invention, a portion of thesemiconductor thin film near the boundary between the oxide electrodefilm and the semiconductor thin film is preferably stacked in anon-reducing atmosphere, and more particularly, in an atmosphere notcontaining hydrogen gas. Typically, the portion of the semiconductorthin film near the boundary between the oxide electrode film and thesemiconductor thin film is stacked by sputtering not using hydrogen gas,and at least another portion of the semiconductor thin film is stackedby plasma enhanced chemical vapor deposition (PE-CVD).

[0037] In the present invention, the semiconductor thin film istypically an amorphous semiconductor thin film, and more specifically,it is a hydrogenated amorphous silicon, a hydrogenated amorphousgermanium, a hydrogenated amorphous silicon germanium, a hydrogenatedamorphous silicon carbide.

[0038] In the present invention, the semiconductor device may basicallybe any that uses a semiconductor thin film. Specifically, however, it isa thin film photovoltaic device, for example, and more particularly, athin film solar battery, for example.

[0039] According to the first aspect of the invention having theabove-summarized structure, since the boundary between the oxideelectrode film and the semiconductor thin film does not contain granularproducts having a diameter of 3 nm or larger, their adherence isimproved. Therefore, when using a base body of a general-purpose plasticlike a polyester film having formed thereon an oxide electrode film likeITO, and stacking thereon a semiconductor thin film by PE-CVD using asource material gas containing hydrogen, the semiconductor thin film canbe effective prevented from peeling off from the base body even if thebase body curves or warps after deposition of the film.

[0040] According to the second and third aspects of the inventionarranged as summarized above, by stacking the semiconductor thin film ina non-reducing atmosphere in an initial period of deposition, it isensured that no granular products having a diameter of 3 nm or largerare contained at the boundary between the oxide electrode film and thesemiconductor thin film, and their adherence is improved. Therefore,when using a base body of a general-purpose plastic like a polyesterfilm having formed thereon an oxide electrode film like ITO, andstacking a semiconductor thin film by PE-CVD using a source material gascontaining hydrogen, the semiconductor thin film can be effectiveprevented from peeling off from the base body even if the base bodycurves or warps after deposition of the film.

BRIEF DESCRIPTION OF THE DRAWINGS

[0041]FIG. 1 is a transmission type electron microscopic image of aregion near the Si:H/ITO boundary of a sample prepared by stacking ana-Si:H film by PE-CVD on an ITO Film stacked on a PET substrate via aSiOx film;

[0042]FIG. 2 is a transparent electron microscopic image of a regionnear the a-Si/ITO boundary of a sample prepared by stacking an a-Si filmby DC sputtering using only Ar gas without using H2 gas on an ITO filmstacked on a PET substrate via a SiOx film;

[0043]FIG. 3 is a schematic diagram showing a result of TEM-EDXmeasurement of the sample shown in FIG. 1;

[0044]FIG. 4 is a schematic diagram showing a result of TEM-EDXmeasurement of the sample shown in FIG. 1;

[0045]FIG. 5 is a cross-sectional view of a thin-film solar batteryaccording to the first embodiment of the invention;

[0046]FIG. 6 is a cross-sectional view of a thin-film solar batteryaccording to the third embodiment of the invention; and

[0047]FIG. 7 is a cross-sectional view of a thin-film solar batteryaccording to the fourth embodiment of the invention[;].

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0048] Explained below are embodiments of the invention with referenceto the drawings.

[0049]FIG. 1 shows a transmission type electron microscopic (TEM) imageof a region distant by about 20 nm in the vertical direction from ITOnear the a-Si:H/ITO boundary of a sample prepared by stacking an a-Si:Hfilm by PE-CVD on an ITO film stacked on a PET substrate via a SiOxfilm. PE-CVD of the a-Si:H film was conducted by flowing 50 sccm ofSiH4/H2 gas under the pressure of 200 mTorr, setting temperature so thatthe substrate temperature Ts is 120 ?C and the RF power to 20W. FIG. 2shows a TEM image of a region distant by about 20 nm in the verticaldirection from ITO near the a-Si/ITO boundary of a sample prepared bystacking an a-Si film by DC sputtering using Ar gas alone without usingH2 gas on an ITO film stacked on a PET substrate via a SiOx film. DCsputtering of the a-Si film was conducted by flowing 50 sccm of Ar gasunder the pressure of 5 mTorr, setting temperature so that the substratetemperature Ts is 80 ?C and the DC power to 1000W.

[0050] Referring to FIG. 1, at the boundary between the a-Si:H film byPE-CVD and ITO, peeling is observed locally, and a region is observedwhere a granular products precipitated at the boundary. As a result ofanalysis through TEM-EDX, this region was confirmed to be a compound ofIn and Sn, and the surface of ITO film reduced and fragile was confirmedto have locally peeled off. From TEM observation, the Inventor is awarethat, when granular products with diameters of and longer than 4 nmexist at the boundary, peeling of the film becomes conspicuous. On theother hand, observing FIG. 2, peeling did not occur at the boundarybetween the a-Si film by sputtering and ITO. This would be because H2gas is not introduced during deposition by sputtering, the ITO surfaceis not exposed to hydrogen ion plasma, and the film is stacked withoutdamaging the surface of the ITO film. According to the knowledgeobtained through TEM observation, no granular products with diameters of3 nm or more were not observed at the boundary.

[0051]FIGS. 3 and 4 show result of TEM-EDX measurement of the sampleshown in FIG. 1. In this TEM-EDX, acceleration voltage is about 200 kV,and the beam diameter is 1 nm. FIG. 3 shows a result with relativelylarge globular products (having a diameter of about [222] 22 nm) whichlay apart from ITO (by a vertical distance around 20 nm), and FIG. 4shows a result with relatively small globular products (having adiameter of about 2 nm) which fully peeled off from ITO. Substantialresolution of this TEM-EDX is considered to have an extension of a beamdiameter not less than 1 nm. In FIG. 3, the reason why many peaks of Siwere detected from globular products with a diameter of about 22 nmpresumably lies in that the acceleration voltage was as high as 200 kV,and there was a high possibility that a lot of information in the depthdirection entered, and it did not mean mixture of Si into the globularproducts. In FIGS. 3 and 4, peaks of Cu are considered to have been madeby Cu in TEM sample holders (mesh), peaks of Cr are considered to havebeen made by a small amount of Cr contained in ITO films, and peaks of Cand O are considered to have been made by impurities absorbed from theatmospheric air during handling of the samples.

[0052] As reviewed above, by stacking an a-Si film by DC sputtering onthe ITO film surface on a plastic substrate without using H2 gas, it ispossible to prevent that granular products, particularly with a diameteraround 4 nm, which cause peeling of films are produced at the boundarywith the base ITO film. More specifically, upon stacking a film ofa-Si:H on an ITO film surface of a plastic substrate, such an a-Si filmby sputtering as a buffer layer largely improves the adherence. Whilethe a-Si:H film is stacked by PE-CVD on a non-hydrogenated a-Si film,the non-hydrogenated a-Si film is [A non-hydride a-Si film is]hydrogenated into a-Si:H film by hydrogen supplied from the a-Si:H film.However, it can be hydrogenated into a-Si:H by diffusing hydrogen later,namely, by first stacking the a-Si film and thereafter annealing theentirety in a hydrogen gas atmosphere.

[0053] This is effective also when an a-Si:H film is stacked on aplastic substrate having formed thereon an oxide electrode materialother than ITO, such as a film of tin oxide, tin oxide doped withfluoric acid, zinc oxide, or the like. This also applies not only toa-Si:H but also to a-Ge:H, a-SiGe:H, and so forth. More generally, itapplies to any semiconductor thin films containing at least one kind ofgroup IV elements.

[0054]FIG. 5 shows a thin-film solar battery according to the firstembodiment of the invention.

[0055] As shown in FIG. 5, in the thin-film solar battery, a transparentinorganic buffer layer 4, transparent electrode film 5, n-type amorphoussemiconductor film 6, i-type amorphous semiconductor film 7, p-typeamorphous semiconductor film 8 and bottom metal reflecting film 9 aresequentially stacked on a transparent organic buffer layer 2 on atransparent plastic base body 3 whose opposite surfaces are hard-coatedby a transparent organic protection film 1 and the transparent organicbuffer layer 2.

[0056] The transparent organic protection film and the transparentorganic buffer layer 2 are of acrylic resin, for example. Thetransparent plastic base body 3 is film-like PET substrate, for example.The transparent electrode layer 5 is made of ITO, for example. Then-type amorphous semiconductor film 6, i-type amorphous semiconductorfilm 7 and p-type amorphous semiconductor film 8 are made of group IVsemiconductors, such as Si. The bottom metal reflecting film 9 is madeof Al, for example.

[0057] A feature of the thin-film solar battery lies in havingsubstantially no granular products made of component elements of thetransparent electrode film 5, or other elements, having diameters of 3nm or larger, and preferably diameters of 1 nm or larger.

[0058] Next explained is a specific example of manufacturing method ofthe thin-film solar battery having the above-explained structure.

[0059] First, as the transparent plastic base body 3 having formed thetransparent organic protection film 1 and the transparent organic bufferlayer 2 on opposite surfaces, there is used a punched-out piece with thediameter of 4 inches from a 200 ?m thick PET substrate, for example,having opposite surfaces hard-coated with acrylic resin, and it iswashed.

[0060] After that, this PET substrate is set in a vacuum chamber of asputtering apparatus, and the chamber is evacuated into about 10-7 Torrby using a vacuum pump. Subsequently, a silicon oxide (SiOx) film isstacked as the inorganic transparent buffer layer 4 on the PET substrateby sputtering. Further, in a similar way, an ITO film is stacked as thetransparent electrode 5 by sputtering. In both these steps, Ar gas isused.

[0061] After that, Ar is supplied by 30 sccm, pressure upon electricdischarge is set at 3 mTorr, temperature is set so that the substratesurface temperature is 120 ?C, plasma is generated with 1000 W, and DCsputtering is conducted by using a target substrate of Si doped withphosphorus to stack a phosphorus-doped n-type a-Si film that is 30 nmthick, for example, as the n-type amorphous semiconductor film 6. Inthis process, the n-type a-Si film on the transparent electrode film 5is stacked by DC sputtering not using H2 gas, and therefore, it isprevented that granular products with diameters of and longer than 1 nmcontaining In or Sn as their major component are produced at theboundary between the transparent electrode film 5 as the ITO film andthe n-type a-Si film.

[0062] After that, in order not to expose the substrate to theatmospheric air, the substrate is transported into the PE-CVD chamber bya loadlock. Subsequently, after setting SiH4 (10%)/H2 to 50 sccm,pressure during electric discharge to 200 mTorr and temperature of thesubstrate surface to 120?C, and generating plasma with the power of 20W, an i-type a-Si:H film, which is 50 nm thick, for example, is stackedas the i-type amorphous semiconductor film 7 on the n-type a-Si film byPE-CVD. Since the thick I-type a-Si:H film used as a photoelectricconversion layer is stacked by PE-CVD, a high deposition rate can beobtained, and the time required for deposition is reduced. The n-typea-Si film as the n-type amorphous semiconductor film 6 is hydrogenatedinto the n-type a-Si:H film by hydrogen supplied from the i-type a-Si:Hfilm during deposition of the i-type a-Si:H film on the n-type a-Si filmby PE-CVD.

[0063] After that, the substrate is again transported into the vacuumchamber of the sputtering apparatus by the loadlock. Then, setting Ar to30 sccm, pressure during electric discharge to 3 mTorr, and temperatureof the substrate surface to 120?C, generating plasma with 1000 W, andDC-sputtering a phosphorus-doped Si target substrate, a phosphorus-dopedp-type a-Si film, which is 30 nm thick, for example, is stacked as thep-type amorphous semiconductor film 8 on the I-type a-Si:H film.

[0064] After that, the substrate is again transported into the vacuumchamber of the sputtering apparatus by the loadlock. Then, supplying Arby 30 sccm onto the p-type a-Si:H film, setting the pressure duringelectric discharge to 3 mTorr and the temperature of the substratesurface to 120?C, generating plasma with 1000 W, and DC-sputtering an Altarget substrate, an Al film, 100 nm thick, for example, is stacked asthe bottom metal reflection film 9.

[0065] Through these steps, the intended thin-film solar battery iscompleted.

[0066] As explained above, according to the first embodiment, since then-type amorphous semiconductor film 6 on the transparent electrode film5 is stacked by DC sputtering not using H2 gas, it is prevented thatgranular products with diameters of and larger than 1 nm at theirboundary, and therefore, adherence of the n-type amorphous semiconductorfilm 6 to the transparent electrode 5 can be enhanced. As a result, evenif the transparent plastic base body 3 curves or warps after depositionof films, separation at the boundary between the transparent electrodefilm 5 and the n-type amorphous semiconductor film 6 can be effectivelyprevented. Thereby, it is possible to realize an amorphous thin-filmsolar battery using a transparent plastic base body 3, which isflexible, light, inexpensive, reliable and efficient. Next explained isa thin-film solar battery according to the second embodiment of theinvention.

[0067] The second embodiment uses an i-type a-SixGel-x:H (O<x?l) film asthe i-type amorphous semiconductor film 7 in the first embodiment. Inthe other respects, it is the same as the first embodiment.

[0068] The manufacturing method of the thin-film solar battery accordingto the second embodiment is the same as the manufacturing method of thethin-film solar battery according to the first embodiment except for thedeposition of the i-type amorphous semiconductor film 7. The i-typea-SixGel-x:H film as the i-type amorphous semiconductor film 7 isstacked in the following manner, for example. That is, supplyingGeH4(10%)/H2 and SiH4(10%)H2, onto the n-type a-Si film, setting thepressure during electric discharge to 200 mTorr and the temperature ofthe substrate surface to 120?C, and thereafter generating plasma withthe power of 20W, a non-doped i-type a-SixGel-x:H (O<x?1) film, which is500 nm thick, for example, is stacked on the n-type Si:H film. In thisprocess, the flow rate ratio between the GeH4(10%)/H2 and SiH4(10%)/H2is gradually changed from the start of deposition so that the ratio of xin the a-SixGel-x:H (0<x?) gradually becomes larger from the substrateside, and from the mid course, SiH4(10%)/H2 is not supplied.

[0069] The second embodiment also has the same advantages as the firstembodiment.

[0070]FIG. 6 shows a thin-film solar battery according to the thirdembodiment of the invention.

[0071] As shown in FIG. 6, in the thin-film solar battery, a transparentinorganic buffer layer 14, transparent electrode film 15, p-typeamorphous semiconductor film 16, i-type amorphous semiconductor film 17,n-type amorphous semiconductor film 18 and bottom metal reflecting film19 are sequentially stacked on a transparent organic buffer layer 12 ona transparent plastic base body 13 whose opposite surfaces arehard-coated by a transparent organic protection film 11 and thetransparent organic buffer layer 12.

[0072] The transparent organic protection film and the transparentorganic buffer layer 12 are of acrylic resin, for example. Thetransparent plastic base body 13 is file-like PET substrate, forexample. The transparent electrode layer 15 is made of ITO, for example.The p-type amorphous semiconductor film 16, i-type amorphoussemiconductor film 17 and n-type amorphous semiconductor film 18 aremade of group IV semiconductors, such as Si. The bottom metal reflectingfilm 19 is made of Al, for example.

[0073] A feature of the thin-film solar battery lies in havingsubstantially no granular products made of component elements of thetransparent electrode film 15, or other elements, having diameters of 3nm or larger, and preferably diameters of 1 nm or larger.

[0074] Next explained is a specific example of manufacturing method ofthe thin-film solar battery having the above-explained structure.

[0075] First, as the transparent plastic base body 13 having formed thetransparent organic protection film 11 and the transparent organicbuffer layer 12 on opposite surfaces, there is used a punched-out piecewith the diameter of 4 inches from a 200 ?m thick PET substrate, forexample, having opposite surfaces hard-coated with acrylic resin, and itis washed.

[0076] After that, this PET substrate is set in a vacuum chamber of asputtering apparatus, and the chamber is evacuated into about 10-7 Torrby using a vacuum pump. Subsequently, a SiOx film is stacked as theinorganic transparent buffer layer 13 on the PET substrate bysputtering. Further, in a similar way, an ITO film is stacked as thetransparent electrode 15 by sputtering. In both these steps, Ar gas isused.

[0077] After that, Ar is supplied by 30 sccm, pressure upon electricdischarge is set at 3 mTorr, temperature is set so that the substratesurface temperature is 120 ?C, plasma is generated at 1000 W, and DCsputtering is conducted by using a target substrate of Si doped withboron to stack a boron-doped p-type a-Si film that is 30 nm thick, forexample, as the p-type amorphous semiconductor film 16. In this process,the p-type a-Si film on the transparent electrode film 15 is stacked byDC sputtering not using H2 gas, and therefore, it is prevented thatgranular products with diameters of and longer than 1 nm containing Inor Sn as their major component are produced at the boundary between thetransparent electrode film 15 as the ITO film and the p-type a-Si film.

[0078] After that, the substrate is transported into the PE-CVD chamberby a loadlock. Subsequently, after setting SiH4 (10%)/H2 to 50 sccm,pressure during electric discharge to 200 mTorr and temperature of thesubstrate surface to 120?C, and generating plasma with the power of 20W, an i-type a-Si:H film, which is 50 nm thick, for example, is stackedas the i-type amorphous semiconductor film 17 on the p-type a-Si film.The p-type a-Si film as the p-type amorphous semiconductor film 16 ishydrogenated into the p-type a-Si:H film by hydrogen supplied from thei-type a-Si:H film during deposition of the i-type a-Si:H film on thep-type a-Si film by PE-CVD.

[0079] Subsequently, supplying SiH4(10%)/H2 by 50 sccm and PH3(1%)/H2 by50 sccm, setting the pressure during electric discharge to 200 mTorr andthe substrate surface temperature to 120?C, and generating plasma withthe power of 20W, a phosphorus-doped n-type a-Si:H film, which is 30 nmthick, for example, is stacked as the n-type amorphous semiconductorfilm 18.

[0080] After that, the substrate is again transported into the vacuumchamber of the sputtering apparatus by the loadlock. Then, supplying Arby 30 sccm onto the p-type a-Si:H film, setting the pressure duringelectric discharge to 3 mTorr and the temperature of the substratesurface to 120?C, generating plasma with 1000 W, and DC-sputtering an Altarget substrate, an Al film, 100 nm thick, for example, is stacked asthe bottom metal reflection film 19.

[0081] Through these steps, the intended thin-film solar battery iscompleted.

[0082] As explained above, according to the first embodiment, since thep-type amorphous semiconductor film 16 on the transparent electrode film15 is stacked by DC sputtering not using H2 gas, it is prevented thatgranular products with diameters of and larger than 1 nm, or 3 nm, attheir boundary, and therefore, [adherence] adhesion of the p-typeamorphous semiconductor film 16 to the transparent electrode 15 can beenhanced. As a result, even if the transparent plastic base body 13curves or warps after deposition of films, separation at the boundarybetween the transparent electrode film 15 and the p-type amorphoussemiconductor film 16 can be effectively prevented. Thereby, it ispossible to realize an amorphous thin-film solar battery using atransparent plastic base body 13, which is flexible, light, inexpensive,reliable and efficient.

[0083]FIG. 7 shows a thin-film solar battery according to the fourthembodiment of the invention.

[0084] As shown in FIG. 7, in the thin-film solar battery, a transparentinorganic buffer layer 24, transparent electrode film 25, p-typeamorphous semiconductor film 26, i-type amorphous semiconductor film 27,n-type amorphous semiconductor film 28 and bottom metal reflecting film29 are sequentially stacked on a transparent organic buffer layer 22 ona transparent plastic base body 23 whose opposite surfaces arehard-coated by a transparent organic protection film 21 and thetransparent organic buffer layer 22.

[0085] The transparent organic protection film and the transparentorganic buffer layer 22 are of acrylic resin, for example. Thetransparent plastic base body 23 is file-like PET substrate, forexample. The transparent electrode layer 25 is made of ITO, for example.The p-type amorphous semiconductor film 26 is made of SiC, which is agroup IV semiconductor, and the i-type amorphous semiconductor film 27and n-type amorphous semiconductor film 28 are made of Si, which is agroup IV semiconductor. The bottom metal reflecting film 29 is made ofAl, for example.

[0086] A feature of the thin-film solar battery lies in havingsubstantially no granular products made of component elements of thetransparent electrode film 25, or other elements, having diameters of 3nm or larger, and preferably diameters of 1 nm or larger.

[0087] Next explained is a specific example of manufacturing method ofthe thin-film solar battery having the above-explained structure.

[0088] First, as the transparent plastic base body 23 having formed thetransparent organic protection film 21 and the transparent organicbuffer layer 22 on opposite surfaces, there is used a punched-out piecewith the diameter of 4 inches from a 200 ?m thick PET substrate, forexample, having opposite surfaces hard-coated with acrylic resin, and itis washed.

[0089] After that, this PET substrate is set in a vacuum chamber of asputtering apparatus, and the chamber is evacuated into about 10-7 Torrby using a vacuum pump. Subsequently, a SiOx film is stacked as theinorganic transparent buffer layer 13 on the PET substrate bysputtering. Further, in a similar way, an ITO film is stacked as thetransparent electrode 15 by sputtering. In both these steps, Ar gas isused.

[0090] After that, Ar is supplied by 30 sccm, pressure upon electricdischarge is set at 3 mTorr, temperature is set so that the substratesurface temperature is 120 ?C, plasma is generated at 1000 W, and DCsputtering is conducted by using a target substrate of SiC doped withboron to stack a boron-doped p-type a-SiC film that is 30 nm thick, forexample, as the p-type amorphous semiconductor film 26. In this process,the p-type a-SiC film on the transparent electrode film 25 is stacked byDC sputtering not using H2 gas, and therefore, it is prevented thatgranular products with diameters of and longer than 1 nm containing Inor Sn as their major component are produced at the boundary between thetransparent electrode film 25 as the ITO film and the p-type a-SiC film.

[0091] After that, the substrate is transported into the PE-CVD chamberby a loadlock. Subsequently, after setting SiH4 (10%)/H2 to 50 sccm,pressure during electric discharge to 200 mTorr and temperature of thesubstrate surface to 120?C, and generating plasma with the power of 20W, an i-type a-Si:H film, which is 50 nm thick, for example, is stackedas the i-type amorphous semiconductor film 17 on the p-type amorphoussemiconductor film. The p-type a-SiC film as the p-type amorphoussemiconductor film 26 is hydrogenated into the p-type a-Si:H film byhydrogen supplied from the i-type a-SiC:H film during deposition of thei-type a-Si:H film on the p-type a-Si film by PE-CVD Subsequently,supplying SiH4(10%)/H2 by 50 sccm and PH3(1%)/H2 by 50 sccm, setting thepressure during electric discharge to 200 mTorr and the substratesurface temperature to 120?C, and generating plasma with the power of20W, a phosphorus-doped n-type a-Si:H film, which is 30 nm thick, forexample, is stacked as the n-type amorphous semiconductor film 28.

[0092] After that, the substrate is again transported into the vacuumchamber of the sputtering apparatus by the loadlock. Then, supplying Arby 30 sccm onto the p-type a-Si:H film, setting the pressure duringelectric discharge to 3 mTorr and the temperature of the substratesurface to 120?C, generating plasma with 1000 W, and DC-sputtering an Altarget substrate, an Al film, 100 nm thick, for example, is stacked asthe bottom metal reflection film 29.

[0093] Through these steps, the intended thin-film solar battery iscompleted.

[0094] The fourth embodiment also has the same advantages as those ofthe third embodiment. In addition to them, it is advantageous inproviding a thin-film solar battery with a higher conversion efficiencybecause it uses the p-type a-SiC film, which is a wide-gapsemiconductor, as the p-type amorphous semiconductor film 26, and allowslight over a wider wavelength band to path through the p-type amorphoussemiconductor film 26 and enter into the i-type amorphous semiconductorfilm 27.

[0095] Although the invention has been explained by way of specificexamples, the invention is not limited to those embodiments, but includevarious changes and modifications within the technical concept of theinvention.

[0096] For example, numerical values, structures, materials, substrates,source materials, processes, and so forth, which were raised in thedescription of the first, second, third and fourth embodiments, are notbut mere examples, and therefore, any other appropriate numericalvalues, structures, materials, substrates, source materials, processes,for example, can be used.

[0097] More specifically, for example, in the first, second, third andfourth embodiments, the a-Si film stacked by sputtering not using H2 gascan be hydrogenated later to form an a-Si:H film.

[0098] As described above, according to the semiconductor deviceproposed by the invention, since granular products as large as andbeyond 3 nm in diameter are not contained substantially at the boundarybetween the oxide electrode film and the semiconductor thin film,adherence of these films is enhanced, and even if the base body curvesor warps after deposition of semiconductor thin films, separation ofsemiconductor thin films from the base body can be prevented. Thereby,it is possible to realize a semiconductor device such as flexiblethin-film solar battery, which uses a general-purpose plastic as itsbase body.

What is claimed is:
 1. A semiconductor device comprising: a base bodymade of an organic high polymer material; an oxide electrode film onsaid base body; and a semiconductor thin film on said oxide electrodefilm, which contains at least one kind of group IV elements, wherein nogranular products each having a diameter not smaller than 3 nm aresubstantially contained at the boundary between said oxide electrodefilm and said semiconductor thin film.
 2. The semiconductor deviceaccording to claim 1 wherein no granular products each having a diameternot smaller than 1 nm are contained at the boundary between said oxideelectrode film and said semiconductor thin film.
 3. The semiconductordevice according to claim 1 wherein said base body is a transparent basebody.
 4. The semiconductor device according to claim 1 wherein saidoxide electrode film is a transparent electrode film.
 5. Thesemiconductor device according to claim 1 wherein said oxide electrodefilm is made of ITO, tin oxide, tin oxide doped with fluoric acid, zincoxide o zinc oxide-aluminum oxide.
 6. The semiconductor device accordingto claim 1 wherein part of said semiconductor thin film near theboundary between said oxide electrode film and said semiconductor thinfilm is stacked in a non-reducing atmosphere.
 7. The semiconductordevice according to claim 1 wherein part of said semiconductor thin filmnear the boundary between said oxide electrode film and saidsemiconductor thin film is stacked in an atmosphere not containinghydrogen gas.
 8. The semiconductor device according to claim 1 whereinpart of said semiconductor thin film near the boundary between saidoxide electrode film and said semiconductor thin film is stacked bysputtering not using hydrogen gas.
 9. The semiconductor device accordingto claim 1 wherein part of said semiconductor thin film near theboundary between said oxide electrode film and said semiconductor thinfilm is stacked in an atmosphere not containing hydrogen gas, and atleast a part of the other part of said semiconductor thin film isstacked by plasma-enhanced chemical vapor deposition.
 10. Thesemiconductor device according to claim 1 wherein said semiconductorthin film is an amorphous semiconductor thin film.
 11. The semiconductordevice according to claim 1 wherein said semiconductor thin film is madeof amorphous silicon hydride, amorphous germanium hydride, amorphoussilicon germanium hydride or amorphous silicon carbide hydride.
 12. Thesemiconductor device according to claim 1 wherein said semiconductordevice is a thin-film photovoltaic device.
 13. The semiconductor deviceaccording to claim 1 wherein said semiconductor device is a thin-filmsolar battery.
 14. A semiconductor device comprising: a base body madeof an organic high polymer material; an oxide electrode film on saidbase body; and a semiconductor thin film on said oxide electrode film,which contains at least one kind of group IV elements, wherein saidsemiconductor thin film is stacked in a non-reducing atmosphere in aninitial period of deposition thereof.
 15. The semiconductor deviceaccording to claim 14 wherein said base body is a transparent base body.16. The semiconductor device according to claim 14 wherein said oxideelectrode film is a transparent electrode film.
 17. The semiconductordevice according to claim 14 wherein said oxide electrode film is madeof ITO, tin oxide, tin oxide doped with fluoric acid, zinc oxide o zincoxide-aluminum oxide.
 18. The semiconductor device according to claim 14wherein part of said semiconductor thin film near the boundary betweensaid oxide electrode film and said semiconductor thin film is stacked ina non-reducing atmosphere.
 19. The semiconductor device according toclaim 14 wherein part of said semiconductor thin film near the boundarybetween said oxide electrode film and said semiconductor thin film isstacked in an atmosphere not containing hydrogen gas.
 20. Thesemiconductor device according to claim 14 wherein part of saidsemiconductor thin film near the boundary between said oxide electrodefilm and said semiconductor thin film is stacked by sputtering not usinghydrogen gas.
 21. The semiconductor device according to claim 14 whereinpart of said semiconductor thin film near the boundary between saidoxide electrode film and said semiconductor thin film is stacked in anatmosphere not containing hydrogen gas, and at least a part of the otherpart of said semiconductor thin film is stacked by plasma-enhancedchemical vapor deposition.
 22. The semiconductor device according toclaim 14 wherein said semiconductor thin film is an amorphoussemiconductor thin film.
 23. The semiconductor device according to claim14 wherein said semiconductor thin film is made of amorphous siliconhydride, amorphous germanium hydride, amorphous silicon germaniumhydride or amorphous silicon carbide hydride.
 24. The semiconductordevice according to claim 14 wherein said semiconductor device is athin-film photovoltaic device.
 25. The semiconductor device according toclaim 14 wherein said semiconductor device is a thin-film solar battery.26. A manufacturing method of a semiconductor device having a base bodymade of an organic high polymer material; an oxide electrode film onsaid base body; and a semiconductor thin film on said oxide electrodefilm, which contains at least one kind of group IV elements, comprising:a step of stacking said semiconductor thin film in a non-reducingatmosphere in an initial period of deposition thereof.
 27. Themanufacturing method of a semiconductor device according to claim 26wherein said base body is a transparent base body.
 28. The manufacturingmethod of a semiconductor device according to claim 26 wherein saidoxide electrode film is a transparent electrode film.
 29. Themanufacturing method of a semiconductor device according to claim 26wherein said oxide electrode film is made of ITO, tin oxide, tin oxidedoped with fluoric acid, zinc oxide o zinc oxide-aluminum oxide.
 30. Themanufacturing method of a semiconductor device according to claim 26wherein said non-reducing atmosphere is an atmosphere not containinghydrogen gas.
 31. The manufacturing method of a semiconductor deviceaccording to claim 26 wherein said semiconductor thin film is stacked bysputtering not using hydrogen gas in an initial period of depositionthereof.
 32. The manufacturing method of a semiconductor deviceaccording to claim 26 wherein sputtering not using hydrogen gas is usedfor deposition of initial part of said semiconductor thin film, andplasma-enhanced chemical vapor deposition is used for deposition of atleast a part of the remainder portion of said semiconductor thin film.33. The manufacturing method of a semiconductor device according toclaim 26 wherein said semiconductor thin film is an amorphoussemiconductor thin film.
 34. The manufacturing method of a semiconductordevice according to claim 26 wherein said semiconductor thin film ismade of amorphous silicon hydride, amorphous germanium hydride,amorphous silicon germanium hydride or amorphous silicon carbidehydride.
 35. The manufacturing method of a semiconductor deviceaccording to claim 26 wherein said semiconductor device is a thin-filmphotovoltaic device.
 36. The manufacturing method of a semiconductordevice according to claim 26 wherein said semiconductor device is athin-film solar battery.